Device for improving water quality

ABSTRACT

Disclosed herein is a device for improving the quality of rainwater/stormwater by removing pollutants therefrom. The device comprises a substantially cylindrical tank having an inlet for entry of liquid and an outlet for discharge of liquid. A coarse filter is provided in the tank for filtering gross pollutants from inflowing liquid, the coarse filter dividing the tank into an upstream first region/chamber and a downstream second region/chamber. A fine pollutant discharge opening is located between the coarse filter and the outlet. A valve comprising a valve member for opening and closing the fine pollutant discharge opening is configured to automatically open the fine pollutant discharge opening to discharge an initial volume of the liquid passing the coarse filter, the valve member being biased toward a configuration for closure of the opening during an inflow event. The liquid passing through opening bypasses the outlet.

TECHNICAL FIELD

The present disclosure relates to a device for improving water quality.The device has been developed primarily for mechanically removingpollutants, such as gross pollutants, organic waste, silt, sediment,nutrients including phosphorous and nitrogen along with hydrocarbonmaterial, oils and the like, from rainwater and stormwater by separationand will be described hereinafter with reference to this application.However, it will be appreciated that the device is not limited to thisparticular application and may also be used for removing pollutants fromother liquid runoff or wastewater, such as for reducing nutrients ordiverting fertilisers from farm runoff, or for removing sediment orother pollutants from water discharged during processing or washing ofvarious items, such as during washing of root vegetables.

BACKGROUND

Various devices exist for removing pollutants, such as litter andsediment above 5 mm in size, from rainwater/stormwater runoff Examplesinclude the gross pollutant traps (GPTs) disclosed in AU2004100956 andWO2007/030735. However, as known GPTs are configured for the removal oflarge pollutants in intense volume water flows, they provide limitedremoval of fine sediment and dissolved pollutants. Also, conventionalGPTs contaminate the whole of the water flow to the highest level of anycontamination passing through the system. Another problem with knownGPTs is that settled contaminants in stormwater collected therein tendto be resuspended by subsequent stormwater inflow.

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in the present specification is not to betaken as an admission that any or all of these matters form part of theprior art base or were common general knowledge in the field relevant tothe present disclosure as it existed before the priority date of eachclaim of this application.

SUMMARY

Throughout this specification:

the word “comprise”, or variations such as “comprises” or “comprising”,will be understood to imply the inclusion of a stated element, integeror step, or group of elements, integers or steps, but not the exclusionof any other element, integer or step, or group of elements, integers orsteps;

the term “inflow event” will be understood to mean an event causing aflow rate of liquid passing the coarse filter to be greater than 5litres per minute or greater than 1.65% of the maximum flow rate throughthe device; and

the term “tank’ will be understood to mean a tank or any other form ofreservoir or enclosure for holding a liquid.

Among other things, disclosed herein is a device for improving waterquality, said device comprising:

a tank;

an inlet for entry of water into the tank;

an outlet for discharge of water from the tank;

a coarse filter in the tank for filtering gross pollutants from waterfed into the tank through the inlet, the coarse filter dividing the tankinto an upstream first region and a downstream second region, the coarsefilter allowing relatively fine pollutants in the water to pass into thesecond region whilst inhibiting relatively coarse pollutants frompassing into the second region, wherein the inlet is associated with thefirst region of the tank and the outlet is associated with the secondregion of the tank;

a bypass mechanism in the tank, the bypass mechanism having a firstconfiguration in which water passing the coarse filter is directed tobypass the outlet, and a second configuration in which water passing thecoarse filter is directed to flow through the outlet, the bypassmechanism:

-   -   being configured to automatically adopt the first configuration        to cause an initial volume of the water passing the coarse        filter to bypass the outlet, and    -   being biased toward the second configuration during an inflow        event.

The bypass mechanism may comprise one or more flow barriers that, in thefirst configuration, direct water passing the coarse filter to flowthrough a bypass opening rather than through the outlet, and that, inthe second configuration, direct water passing the coarse filter to flowthrough the outlet.

The one or more flow barriers may comprise a valve member of one or morevalve and/or one or more gate.

The bypass mechanism may be configured to move between the first andsecond configurations in response to a force, such as buoyancy, applieddirectly or indirectly to the one or more flow barriers by at least aproportion of the water entering the device through the inlet. Thedevice may comprise one or more drain openings for drainage of waterafter an inflow event to relieve the force applied to the one or moreflow barriers by the water and thereby to facilitate resetting thebypass mechanism to the first configuration.

In the second configuration, the one or more flow barriers may close, orat least substantially close, the bypass opening and/or open the outlet,and in the first configuration, the one or more flow barriers may openthe bypass opening and/or close the outlet. The one or more flowbarriers may be configured to cause at least part of the water flowpassing the coarse filter to bypass the outlet if a predetermined weightof fine pollutants accumulates on the one or more flow barriers.

The one or more flow barriers may comprise a float to facilitateautomatically moving the bypass mechanism between the first and secondconfigurations. The float may be part of the one or more flow barriers.The float may be housed in a float chamber that receives at least partof the initial volume of the water passing the coarse filter, such thatinflow of water into the float chamber facilitates raising the float andmoving the bypass mechanism to the second configuration. In a firstfamily of embodiments, with the bypass mechanism in the firstconfiguration, said at least part of the initial volume of the waterpassing the coarse filter may flow to the float chamber via the bypassopening. The float chamber may have one or more drain openings thereinfor draining water from the float chamber. In a second family ofembodiments, the one or more flow barrier may comprise: a valve memberbiased into sealing engagement with the outlet, such as by gravityand/or by a spring; and a container for receiving at least part of theinitial volume of the water passing the coarse filter, the containerbeing configured to move between a first configuration and a secondconfiguration as water accumulates therein, wherein the container isconnected to the valve member, for example by a tether, such that, withthe bypass mechanism in the first configuration, accumulation of waterin the container causes the container to move, thereby moving the valvemember out of sealing engagement with the outlet to define the secondconfiguration of the bypass mechanism. The container may have one ormore drain openings therein for draining water from the container. Whenthe container is in the second configuration, it acts as a gate forsubstantially preventing water passing the coarse filter from flowingthrough the bypass opening. The valve member biased into sealingengagement with the outlet may be buoyant and may, along with theaccumulation of water in the container, facilitate automatically movingthe bypass mechanism between the first and second configurations. Ineither family of embodiments, drainage of water through the one or moredrain openings may reset the bypass mechanism to the first configurationafter an inflow event. The one or more drain openings may have acombined area that allows the float to rise during an inflow event.

The device may be configured such that the bypass mechanism is delayedfrom adopting the second configuration:

for a predetermined time, which may be greater than 1 minute and lessthan 5 minutes, and in some embodiments may be around 2 minutes, fromcommencement of an inflow event of at least the same duration; or

until a predetermined initial volume of water, such as an initial volumeof between 0.3 m³ and 0.9 m³ of water, has been discharged aftercommencement of an inflow event of at least the same volume, or untileach square metre of the catchment served by the device has received, onaverage, greater than 1.2 mm of precipitation that reaches the device.

In the first family of embodiments, the volume of the float chamber maygovern the delay in the bypass mechanism adopting the secondconfiguration In the second family of embodiments, a relationshipbetween the rate at which water accumulates in the container and themagnitude of the force(s) biasing the valve member toward sealingengagement with the outlet governs the delay in the bypass mechanismadopting the second configuration.

In the first family of embodiments, one or more restricted openings maybe provided in or around the one or more flow barriers to allow waterthat has passed the coarse filter to pass into the float chamber whenthe valve is in the second configuration. The combined area of the oneor more restricted openings may be substantially equal to the combinedarea of the one or more drain openings. The float may have a buoyancyselected to cause the one or more flow barriers to at least partiallyopen the bypass opening if a predetermined weight of fine pollutantsaccumulates on the one or more flow barriers.

In the first family of embodiments, the inlet may be oriented to directwater entering the tank to flow in a substantially spiral path around acylindrical wall of the first region. The inlet may be curved with aradius similar to that of the first region to provide a smoothtransition for water entering the first region.

In the first family of embodiments, an upstream surface of the coarsefilter may be sloped to direct relatively coarse pollutants toward acoarse pollutant discharge opening. The upstream surface of the coarsefilter may be substantially concave and a coarse pollutant dischargeopening may be located substantially centrally on the concave surface.The upstream surface of the coarse filter may be substantially conical.One or more substantially spiral vanes or channels may be formed on theupstream surface of the coarse filter. The coarse pollutant dischargeopening may comprise a discharge chute that extends longitudinallythrough the second region. In embodiments with a float chamber, thedischarge chute may also extend longitudinally through the floatchamber. The fine pollutant discharge opening may be annular anddisposed around the discharge chute. The coarse pollutant dischargeopening may direct coarse pollutants to a sump. The bypass opening maydischarge into the sump.

In the second family of embodiments, the coarse filter may be shaped toslow the velocity of water entering the device. The upstream surface ofthe coarse filter may define one or more channel into which waterentering the device is directed. The channels may direct relativelycoarse pollutants in the water toward a coarse pollutant dischargeopening. The inlet and the coarse pollutant discharge opening may be atopposite ends of the device.

A fine filter may be provided downstream of the coarse filter to filterrelatively fine pollutants in water passing from the second region tothe outlet. The fine filter may have openings therein configured tocapture pollutants sized greater than 0.4 mm, greater than 0.5 mm,greater than 0.6 mm, greater than 0.7 mm, greater than 0.8 mm, greaterthan 0.9 mm or greater than around 1 mm. The fine filter may comprise a0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm or around 1 mm meshscreen. The fine filter may comprise a 40-210 micron screen, which maybe a nylon sieve mesh fabric screen. In the first family of embodiments,the fine filter may extend substantially circumferentially within thesecond region. In the second family of embodiments, the fine filter maybe provided immediately upstream of the valve member biased into sealingengagement with the outlet and may be at least partially defined byperforated walls of a valve chamber in which the valve member is housed.

The coarse filter may have openings therein configured to capturepollutants greater than a predetermined size. The openings in the coarsefilter may be 5 mm in diameter. Hoods may extend partially over openingsin the coarse filter. The hoods may extend from the downstream end ofthe openings in the coarse filter and on the downstream side of thecoarse filter. The hooded openings may have a configuration similar tothose of a cheese grater.

The device may comprise an access opening to the first region forfacilitating removal of captured gross pollutants, access to internalcomponents of the device for maintenance, and/or removal of internalcomponents for flushing out of the device on commissioning. A removablelid may cover the access opening. A safety barrier may extend across theaccess opening below the lid to restrict personal entry into the device.The lid may be sufficiently strong to support the weight of motorvehicles. The lid may have a lock mechanism to restrict access without acorresponding access tool, such as a key. The access tool may becaptively engaged with the lock mechanism when it is unlocked to preventremoval of the access tool until the lock mechanism is re-locked. Thelock mechanism may be configured not to re-lock unless the lid isclosed. The lock mechanism may be configured to hold the lid in place ifthe first region fills with water and applies pressure to the undersideof the lid, for example in extreme inflow events or in the case of ablockage in or downstream of the device.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a first perspective view of a first embodiment of a waterquality improvement device in accordance with the present disclosure;

FIG. 2 is a second perspective view of the device of FIG. 1;

FIG. 3 is a third perspective view of the device of FIG. 1;

FIG. 4 is a cross sectional view through the device of FIG. 1, taken ina plane containing lines 4 and looking in the direction of lines 5 ofFIG. 1, shown with its fine pollutant discharge opening open ready foran inflow event;

FIG. 5 is a cross sectional view through the device of FIG. 1, taken ina plane containing lines 5 and looking in the direction of lines 4 ofFIG. 1, shown with its fine pollutant discharge opening closed during aninflow event;

FIG. 6 is an enlarged perspective view of the coarse filter of thedevice of FIG. 1;

FIG. 7 is a perspective view of a second embodiment of a water qualityimprovement device in accordance with the present disclosure;

FIG. 8 shows a central vertical longitudinal cross section of the deviceof FIG. 7, wherein the device is shown with its bypass opening openready for an inflow event;

FIG. 9 shows a central vertical transverse cross section of the deviceof FIG. 7, wherein the device is shown with its bypass opening openready for an inflow event;

FIG. 10 shows a top perspective view of the device of FIG. 7, whereinthe top of the tank is cut away to allow internal components to be seen;and

FIG. 11 shows a top perspective view of the device of FIG. 7, whereinparts of the device above a lower extremity of the coarse filter are cutaway to allow parts below the coarse filter to be seen.

DETAILED OF EMBODIMENTS

Referring to the drawings, and initially to FIGS. 1-6, there is shown awater quality improvement device 10 for removing pollutants fromstormwater. The device 10 comprises a substantially cylindrical tank 12defining a longitudinal axis A that is oriented vertically in use. Aninlet 14 and an outlet 16, respectively for entry and discharge ofstormwater to and from the tank 12 are provided.

A coarse filter 18 extends diametrically across the tank and divides thetank 12 into an upstream first region/chamber 20 and a downstream secondregion/chamber 22. Openings 18 a in the upstream end of the coarsefilter 18 are configured to inhibit or “trap” gross pollutants in thestormwater sized greater than around 5 mm, whilst allowing thestormwater and smaller pollutants therein to pass into the secondregion/chamber 22. The openings 18 a are hooded, having a form similarto the openings of a cheese grater, with the hoods of the openings 18 aextending on the downstream side of the coarse filter 18 and from thedownstream end of the openings 18 a. The upstream surface of the coarsefilter 18 is substantially conical, tapering to a central coarsepollutant discharge opening 24. A discharge chute 26 extends from thedischarge opening 24 longitudinally through the second chamber 22 andinto a sump 28. Substantially spiral vanes or channels 30 are formed onthe upstream surface of the coarse filter 18. Due to gravity, grosspollutants captured by the coarse filter fall down the conical surfaceand through the discharge opening 24 and chute 26 into the sump 28.

A fine filter 32 extends substantially circumferentially within thesecond chamber 22 to inhibit or “trap” relatively fine pollutants sizedgreater than around 0.5 mm to 1 mm from stormwater passing through thecoarse filter 18, whilst allowing the stormwater and smaller ordissolved pollutants therein to pass to the outlet 16. The fine filtermay comprise a 1 mm mesh screen and/or a 40-210 micron nylon sieve meshfabric screen.

An annular bypass opening 34 is provided in the base 22 a of the secondchamber 22, around the discharge chute 26. The bypass opening 34 islocated downstream of the coarse filter 18 and upstream of the outlet16. Stormwater passing through the bypass opening 34 bypasses the outlet16.

A bypass mechanism/valve 36 comprising a valve member 36 a is providedfor opening and closing the fine pollutant discharge opening 34. Thevalve member 36 a takes the form of a buoyant float housed in a floatchamber 38. The valve member 36 a is slidably mounted on spindles 36 b,which extend longitudinally through the float chamber to guide the valvemember 36 a as it moves between an open and closed configuration. Thevalve member 36 a and float chamber 38 are annular, with an inner wallof the float chamber 38 being defined by the discharge chute 26, whichextends longitudinally through the float chamber. With the valve 36open, the second chamber 22 and the float chamber 38 are in fluid flowcommunication via the fine pollutant discharge opening 34. The floatchamber 38 has a plurality of drain openings 40 therein for draining thefloat chamber after an inflow event, thereby to reset the valve 36 to anopen configuration for a future inflow event. Stormwater passing throughthe drain openings 40 passes into the sump 28. The drain openings 40have a combined area selected to cause the valve member 36 a to riseduring an inflow event. The combined area of the drain openings 40,along with the volume of the float chamber 38, are selected to cause thefine pollutant discharge opening 34 to remain open for around 2 minutes,depending on the inflow rate, until an initial volume of approximately0.3 m³ to 0.9 m³ of stormwater has been discharged after commencement ofan inflow event of at least the same duration or until each square metreof the catchment served by the device 10 has received, on average,greater than 1.2 mm of precipitation/inflow that reaches the device.During this time interval, the valve member 36 a buoyantly rises toclose the pollutant discharge opening 34. If the inflow rate into thedevice 10 is less than 5 L/min, or less than 1.65% of the maximum flowrate through the device, the inflow may contain a relatively highconcentration of dissolved pollutants. In such low flows, the valvemember 36 a will not rise such that the valve 36 and fine pollutantdischarge opening 34 remain open to allow the polluted inflow to bypassthe outlet 16 for treatment by another method before being dischargedback as an environmental flow.

A restricted opening 42 is provided between the valve member 36 a andthe fine pollutant discharge opening 34 to allow stormwater to pass at aslow rate from the second chamber 22 into the float chamber 38 when thevalve 36 is closed. The area of the restricted opening 42 issubstantially equal to or greater than the combined area of the drainopenings 40 to maintain the float chamber 38 full during an inflow eventwithout requiring the valve 36 to open. However, the valve member 36 ahas a buoyancy selected to cause the valve 36 to at least partially openif a predetermined weight of fine pollutants accumulates on the valvemember 36 a, and thereby to discharge the accumulated fine pollutantsinto the sump 28 via the float chamber 38.

The inlet 14 is oriented to direct stormwater entering the tank 12 toflow in a substantially spiral path around the wall of the first chamber20. The inlet 14 is curved with a radius similar to that of the firstchamber 20 to provide a smooth and hydrodynamic slowing transition asstormwater enters the first chamber 20 from the inlet 14.

The device 10 comprises a removable lid 44 to facilitate removal ofcaptured gross pollutants. The lid 44 covers an access opening 46 in thefirst chamber 20, through which gross pollutants and stormwater can beextracted from the sump 28. The lid 44 is sufficiently strong to supportthe weight of motor vehicles. The lid 44 also facilitates removal of oraccess to internal components of the device 10 for maintenance and/orremoval of internal components for flushing out of the device oncommissioning. A removable safety barrier may be extend across theaccess opening 46 below the lid to prevent unauthorised or accidentalpersonal entry into the device 10, including entry by children, when thelid 44 is removed.

The lid 44 may have a lock mechanism to restrict access without acorresponding access tool, such as a key. The access tool may becaptively engaged with the lock mechanism when it is unlocked to preventremoval of the access tool until the lid 44 is closed and the lockmechanism is re-locked. The lock mechanism may be configured to hold thelid 44 in place if the first chamber 20 fills with liquid and appliespressure to the underside of the lid, for example in extreme inflowevents or in the case of a blockage in or downstream of the device 10.

It will be appreciated that the illustrated device 10 providessignificant advantages over conventional GPTs and other water qualityimprovement devices. In particular, the device 10 significantly improvesthe removal of fine contaminants, including sediment and dissolvedpollutants, from stormwater by automatically dumping the initial inflowfollowing an inflow event, which tends to contain a higher concentrationof fine contaminants, and periodically dumping fine contaminants thataccumulate on the valve member 36 a. This form of separation reduces theloading of pollutants carried by the stormwater passing through outlet16, such that a substantially lower volume of pollutants need to betreated or filtered by a downstream process prior to the waste streambeing released to a receiving waterway. The device 10 also facilitates agreater volume of stormwater harvested being directed to storage,compared to a conventional GPT that does not syphon off an initial,often highly polluted, volume of stormwater. Such conventional GPTsdisadvantageously contaminate all of the collected stormwater with theoften highly polluted initial inflow. The automatic resetting of thevalve 36 to its open configuration after an inflow event, and in lowinflow situations, advantageously ensures that the device 10 is ready todump the initial portion of a future inflow event and also allowscontinued removal of pollutants even when the flow is impractical toharvest.

The hoods on the downstream side of openings 18 a in the coarse filter18 advantageously reduce the build-up of pollutants such as paper andsinuous/fibrous material on the coarse filter 18 by creating a ramp thatguides coarse pollutants thereover to facilitate self-cleaning, whilstallowing water and fine pollutants to drain into the second chamber 22.Without the hooded openings 18 a, coarse pollutants may catch on thedownstream edge of the coarse filter openings and gradually accumulateand cause obstruction, thereby blocking the device 10, reducing itsefficiency and requiring more regular maintenance. It will also beappreciated that the spiral vanes/channels 30 advantageously hold lowerwater flows in the coarse filter 18 for a longer period to increasepollutant capture rate in low intensity inflows. The spiralvanes/channels 30 are also intended to improve the hydrodynamic actionof the inflow, holding the water stream in the coarse filter 18 for aslong as possible to increase the volume of water passing into the secondchamber 22. The spiral vanes/channels 30 are also intended to dislodgepollutants that may accumulate on the upstream side of the coarse filter18, and to generally facilitate flow of larger pollutant materialdownwards towards the discharge opening 24 and chute 26.

The device 10 also facilitates a distributed micro system of stormwatercapture that concentrates the catchment contamination in the area ofoperation serviced by the device 10. The device 10 will further allowthe potential for stormwater drainage to be at or near surface levelfiltration and separation, it will enable a moderate reduction ormitigation of flooding and the effects of widespread contamination of aflooding event in major streams and canals, wetlands and rivers. Thedevice 10 can also facilitate the collection and redirection ofpollutants to a holding cavity as a retention/delayed system ofstormwater release, the device 10 being an independent device notreliant on catchment overflows, thereby better managing the water cyclein rainfall through to flooding events when applied to the designspecification of Annual Recurrent Intensity rainfall events. The device10 can also be configured for use with roof capture systems forprotected catchments.

Reference is now made to FIGS. 7-11 of the drawings, which show a waterquality improvement device 10′ having a number of features in commonwith the device 10 of FIGS. 1-6, where corresponding reference numeralsindicate corresponding features with corresponding functionality. Thedevice 10′, however, is reconfigured in a rectangular arrangement,having its longitudinal axis extending horizontally, in use, rather thanvertically as is the case with device 10.

In device 10′, the coarse filter 18 is shaped to slow the velocity offluid entering the device. Specifically, the upstream surface of thecoarse filter 18 defines a central mound 18 b extending longitudinallythrough the tank and a channel 18 c on each lateral side of the mound.Fluid entering the device 10′ through inlet 14 and/or opening 46 isdivided by the mound 18 b and directed into the channels 18 c. Thechannels 18 c direct relatively coarse pollutants in the fluid towardcoarse pollutant discharge opening 24. It will be appreciated thatcoarse filter 18 acts as a hydrodynamic separator that separatesrelatively coarse pollutants from the inflow water by slowing thevelocity of the water entering the device, thereby increasing the timethat the inflowing water stream is in the first region/chamber 20, andthereby increasing the volume of water with the relatively coarsepollutants removed passing through the coarse filter 18 into the secondregion/chamber 22. As shown, the inlet 14 and the coarse pollutantdischarge opening 24 are at opposite longitudinal ends of the device10′. The floor of channels 18 c is angled relative to horizontal towardthe coarse pollutant discharge opening 24. A platform 50 is providedbelow the coarse filter 18 and is angled relative to horizontal awayfrom the coarse pollutant discharge opening 24. A container 52 ishingedly connected to an end of the platform 50 closest the coarsepollutant discharge opening 24, extends from side to side of the tank12, and is moveable between a first configuration in which it iselevated from the floor of tank 12 and a second configuration in whichit engages the floor of tank 10. In the second configuration, thecontainer 52 acts as a gate extending across the tank 12 and preventingfluid passing the coarse filter 18 from flowing to the coarse pollutantdischarge opening 24. One or more fluid conduits, in the form ofchannels 54 extending from the channels 18 c, direct a portion of fluidentering the device 10′ to the container 52.

The coarse filter 18 and fine filter 32 of device 10′ have openings ofthe same size as those of coarse filter 18 and fine filter 32 of device10. In device 10′, an additional fine filter 60 of 0.4 mm mesh isprovided in the base of channels 18 c.

Device 10′ comprises a bypass mechanism that includes two flow barriers,in the form of a valve member 56 and container 52. The valve member 56is biased by its self-weight and/or a spring (not shown) into sealingengagement with the outlet 16. The container 52 is connected to thevalve member 56 by a tether 58. Accumulation of fluid in the container52 causes the container to move from its elevated first configuration toits lowered second configuration against the bias of the valve member 56toward the outlet 16. Lowering of the container 52 raises the valvemember 56 out of sealing engagement with the outlet 16 to define thesecond configuration of the bypass mechanism in which fluid passing thecoarse filter 18 is blocked from flowing to opening 24 by thecontainer/gate 52 and instead is allowed to pass through open outlet 16due to the valve member 56 being raised. In some embodiments, valvemember 56 is buoyant, such that buoyancy of the valve member 56 togetherwith accumulation of liquid in the container 52 facilitate automaticallymoving the bypass mechanism 52, 56 between its first and secondconfigurations.

The container 52 has one or more drain openings (not shown) therein fordraining liquid from the container 52. As with the drain openings 40 ofdevice 10, the one or more drain openings of device 10′ have a combinedarea that allows the bypass mechanism to move into its secondconfiguration by allowing liquid to accumulate in the container 52during an inflow event and, after an inflow event, the drain openings 40allow drainage of liquid from the container 52 to reset the bypassmechanism to its first configuration.

In device 10′, a relationship between the rate at which fluidaccumulates in the container 52 and the magnitude of the self-weight andspring force biasing the valve member 56 toward sealing engagement withthe outlet 16 governs the delay in the bypass mechanism 52, 56 adoptingthe second configuration. Similarly to device 10, this delay is foraround 2 minutes, depending on the inflow rate, until an initial volumeof approximately 0.3 m³ to 0.9 m³ of stormwater has been dischargedafter commencement of an inflow event of at least the same duration oruntil each square metre of the catchment served by the device 10′ hasreceived, on average, greater than 1.2 mm of precipitation/inflow thatreaches the device. During this time interval, the container/gate 52lowers to close opening 34 and valve member 56 rises to open outlet 16.If the inflow rate into the device 10′ is less than 5 L/min, or lessthan 1.65% of the maximum flow rate through the device, the inflow maybe highly with dissolved pollutants. In such low flows, thecontainer/gate 52 will not lower and valve member 56 will not rise, suchthat the polluted inflow bypasses the outlet 16 and passes throughopening 34 under container/gate 52 for discharge through opening 24.

Persons of skill in the art will recognise that device 10′ shares manyof the applications and advantages discussed above with regard to device10.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the above-describedembodiments, without departing from the broad general scope of thepresent disclosure. The present embodiments are, therefore, to beconsidered in all respects as illustrative and not restrictive. Examplesof possible variations and/or modifications include, but are not limitedto:

-   -   the coarse filter 18 of device 10 being hemi-spherical or        another concave shape, or being planar, or being cylindrical;    -   the coarse filter 18 of device 10′ being another shape;    -   the valve 36 may be resiliently biased toward the closed        configuration by a mechanical spring rather than, or in addition        to, by buoyancy and may be automatically actuated to discharge        fine pollutants by weight of inflowing water;    -   instead of a valve being open to cause fluid in the device 10 to        bypass the outlet 16, as is the case with valve 36, a variation        of device 10 may require a valve to be closed to cause fluid to        bypass the outlet 16 and, in such a variation, buoyancy of the        valve member, alone or aided by other means, may cause the valve        to open, optionally against the bias of a mechanical spring, to        cause fluid flowing through the device to flow through the        outlet;    -   rather than having an open and closed configuration as such, the        valve 36 may instead be configured to move between a first        configuration in which it directs liquid passing the coarse        filter 18 to bypass the outlet 16 and a second configuration in        which it directs liquid passing the coarse filter to flow        through the outlet 16;    -   the lid 44 may comprise a grate or other opening(s) to allow        direct inflow from the head of the tank 12 instead of or in        combination with the inlet 14;    -   an upper portion of the device 10 may comprise a riser section        to vary the inlet pipe positioning by nominally 100 mm        increments;    -   a plurality of the devices 10, 10′ can be used to increase the        performance of a catchment stormwater flow management system;        and/or    -   using the device 10 in combination with a downstream device        optimised to remove pollutants remaining in the stormwater        passing through outlet 14.

What is claimed is:
 1. A device for improving water quality, said devicecomprising: a tank; an inlet for entry of water into the tank; an outletfor discharge of water from the tank; a coarse filter in the tank forfiltering gross pollutants from water fed into the tank through theinlet, the coarse filter having an upstream end and a downstream end,the coarse filter dividing the tank into an upstream first region and adownstream second region, the coarse filter allowing relatively finepollutants in the water to pass into the second region whilst inhibitingrelatively coarse pollutants from passing into the second region,wherein the inlet is associated with the first region of the tank andthe outlet is associated with the second region of the tank; a bypassmechanism in the tank, the bypass mechanism including one or more flowbarriers having a first configuration and a second configuration inwhich in the first configuration the one or more flow barriers directwater passing the coarse filter to bypass the outlet and instead flowthrough a bypass opening and in which in the second configuration theone or more flow barriers direct water passing the coarse filter tobypass the bypass opening and instead flow through the outlet, the waterpassing through the bypass opening in the first configuration beingquarantined from the water passing through the outlet in the secondconfiguration and the bypass mechanism: being configured toautomatically adopt the first configuration to cause an initial volumeof the water passing the coarse filter to bypass the outlet, and beingbiased toward the second configuration during an inflow event; a coarsepollutant discharge opening located at the downstream end of the coarsefilter and through which gross pollutants filtered by the coarse filterare discharged; and a divider in the first region to form a plurality ofchannels in the first region, each of the channels extending between theinlet and the coarse pollutant discharge opening.
 2. The device of claim1, wherein an upstream surface of the coarse filter defines the divider.3. The device of claim 1, wherein the bypass mechanism comprises: avalve member biased toward sealing engagement with the outlet; acontainer connected to the valve member by a tether, the containercomprising a drain for drainage of the container after a said inflowevent; and a fluid flow pathway for directing a portion of the waterpassing the coarse filter to the container, wherein accumulation ofwater in the container causes the container to move from a firstposition to a second position, thereby moving the valve member out ofsealing engagement with the outlet.
 4. The device of claim 3, wherein:in its first position, the container allows water passing the coarsefilter to flow to the coarse pollutant discharge opening; and in itssecond position, the container blocks water passing the coarse filterfrom flowing to the coarse pollutant discharge opening and directs thewater to the outlet.
 5. The device according to claim 1, wherein thebypass mechanism is configured to move between the first and secondconfigurations in response to a force applied directly or indirectly tothe one or more flow barriers by at least a proportion of the waterentering the device through the inlet.
 6. The device according to claim5, comprising one or more drain openings for drainage of water after aninflow event to relieve the force applied to the one or more flowbarriers by the water and thereby to facilitate resetting the bypassmechanism to the first configuration.
 7. The device according to claim1, the device being configured such that the bypass mechanism is delayedfrom adopting the second configuration for a predetermined time fromcommencement of an inflow event of at least the same duration.
 8. Thedevice according to claim 1, the device being configured such that thebypass mechanism is delayed from adopting the second configuration untila predetermined initial volume of water entering the device has bypassedthe outlet after commencement of an inflow event of at least the samevolume, or until each square metre of a catchment served by the devicehas received, on average, greater than 1.2 mm of precipitation thatreaches the device.
 9. The device according to claim 1, comprising afine filter downstream of the coarse filter to filter relatively finepollutants in water passing from the second region to the outlet. 10.The device according to claim 9, wherein the fine filter comprisesopenings therein configured to capture pollutants sized greater than 0.4mm to 1 mm.
 11. The device according to claim 9, wherein the fine filtercomprises a 1 mm mesh screen.
 12. The device according to claim 9,wherein the fine filter comprises a 40-210 micron screen.
 13. The deviceaccording to claim 9, wherein the coarse filter comprises openingslarger than the openings of the fine filter.
 14. The device according toclaim 1, wherein the coarse filter comprises openings of approximately 5mm in diameter.
 15. The device of claim 1, wherein the coarse filterdefines the divider, the coarse filter being configured to slow thevelocity of the water in the first region and thereby to increase adwell time of the water in the first region.